Patent Application
20240217064
This Nonprovisional application claims priority under 35 U.S.C. § 119 on Patent Application No. 2022-212829 filed in Japan on Dec. 29, 2022, the entire contents of which are hereby incorporated by reference.
The present invention relates to a shot-blasting device, a control method, and a control program.
A technique is conventionally known in which in order to manage a shot quality, a shot amount is adjusted in a shot-blasting device so that a motor current value of an impeller falls within a certain range.
[Patent Literature 1]
Japanese Patent Application Publication Tokukaihei No. 06-143147
Technical Problem
However, the certain range can be set only within a limit of accuracy of adjustment of the shot amount. In a conventional technique, only a shutter plate or a gate and a cylinder are used to adjust the shot amount. This makes it impossible to finely adjust a degree of opening of the shutter plate or the gate. Thus, in the conventional technique, accuracy is too insufficient to set a range of a motor current value of an impeller to the extent that allows (i) determination of a lower limit of the shot amount for satisfying a reference quality or (ii) determination of an upper limit of the shot amount for preventing an excessive load from being applied to a component. Thus, even in a case where the motor current value of the impeller is within the certain range, a defective product may be produced, and/or excessive projection may be carried out.
An aspect of the present invention has an object to adjust a lower limit of a shot amount with high accuracy.
In order to attain the object, a shot-blasting device in accordance with an aspect of the present invention includes: a distributor that has at least one gate and that supplies a blasting medium; an impeller that has at least one motor and that projects the blasting medium which has been supplied via the at least one gate; at least one processor; at least one cylinder that opens and closes the at least one gate; and at least one servo motor that changes a position of the at least one cylinder, the at least one processor adjusting a degree of opening of the at least one gate, by subjecting the at least one cylinder in a state of opening the at least one gate to position control with use of the at least one servo motor, so that a load current value of the at least one motor of the impeller falls within a set range having a lower limit.
A shot-blasting device in accordance with each aspect of the present invention can be realized by a computer. In this case, the scope of the invention also encompasses (i) a shot-blasting device control program for causing the computer to realize the shot-blasting device by causing the computer to operate as sections (software elements) of the shot-blasting device and (ii) a computer-readable storage medium recording the shot-blasting device control program.
According to the above description, it is possible to adjust a lower limit of a shot amount with high accuracy, and a probability with which a defective product will be produced can be reduced by properly maintaining a projection quality.
First, the following description will discuss an overview of embodiments of the present disclosure.
(Item 1) A shot-blasting device including:
(Item 2) The shot-blasting device described in item 1, wherein the set range further has an upper limit.
(Item 3) The shot-blasting device described in item 1 or 2, wherein
(Item 4) The shot-blasting device described in any one of items 1 to 3, further including a storage section,
(Item 5) The shot-blasting device described in item 4, wherein the lower limit is stored while the shot-blasting device is in operation.
(Item 6) The shot-blasting device described in item 4 or 5, wherein the at least one processor reads the stored lower limit from the storage section and sets the lower limit.
(Item 7) The shot-blasting device described in item 6, wherein the lower limit is set before operation of the shot-blasting device commences.
(Item 8) The shot-blasting device described in any one of items 4 to 7, wherein the storage section further stores the degree of opening of the at least one gate as time series data.
(Item 9) A method for controlling a shot-blasting device, the shot-blasting device including:
(Item 10) A program for causing a computer including the at least one processor to function as a shot-blasting device described in item 1, the program causing the at least one processor to carry out the position control.
The following description will specifically discuss an embodiment of the present invention.
The following description will discuss, with reference to (a) and (b) of
The shot-blasting device 1 includes, as illustrated in (a) of
The blasting medium 400 is exemplified by spherical metallic particles (so-called shots) and acute-angled metallic particles (so-called grids). Alternatively, the blasting medium 400 may be particles of nonmetals (e.g., glass, ceramics, sand, resins, or plant seeds). The projection target object 500 is, for example, an industrial product such as a casting.
The projecting device 100 is constituted by, for example, (i) the distributor 110 that supplies the blasting medium 400 to an impeller 120 and (ii) the impeller 120 that projects, to the projection target object 500, the blasting medium 400 supplied from the distributor 110. Note, however, that the projecting device 100 may include other part(s) (not illustrated). The blasting medium 400 that has been projected may be collected by, for example, a bucket elevator (not illustrated) and supplied to the distributor 110 again.
The distributor 110 supplies the blasting medium 400 to the impeller 120 so that the blasting medium 400 is projected in an amount sufficient to maintain a proper projection density (described later). The distributor 110 includes a gate 111 that adjusts an amount of supply of the blasting medium 400. The gate 111 includes a cylinder 112 and a servo motor 113. The cylinder 112 is switchable between a state of opening the gate 111 and a state of closing the gate 111. When the cylinder 112 is in the state of closing the gate 111, the gate 111 is in a closed state. When the cylinder 112 is in the state of opening the gate 111, the gate 111 is in an open state. In a case where the gate 111 is in the closed state, no blasting medium 400 is supplied to the impeller 120. In a case where the gate 111 is in the open state, the blasting medium 400 is supplied to the impeller 120. A degree of opening of the gate 111 can be adjusted by causing the servo motor 113 to change a position of the cylinder 112 that is in the state of opening the gate 111.
A gate-type flow control device commonly controls a volume in which powder and particles flowing through an opening cross section flow continuously. The gate-type flow control device has a disadvantage such that it is difficult to achieve exactly the same flow rate due to various factors such as (i) a bulk density and fluidity of powder during a flow of powder and particles under gravity, (ii) a particle size configuration of powder and particles, typified by an angle of repose of powder and particles, and (iii) a difference in powder and particle shape. However, the gate-type flow control device, which has a simple configuration and is industrially inexpensive, is suitable for flow control carried out at a flow rate obtained by averaging flow rates for a certain period of time. Thus, the gate-type flow control device is widely adopted.
In a shot-blasting process, the blasting medium 400 that has been used for projection has a problem of being more worn than before projection due to collision and/or friction with, for example, the projection target object 500. The projecting device 100 collects the blasting medium 400 that has been projected, and uses, for example, a wind force to exclude the blasting medium 400 that is not suitable to be reused. Thereafter, the projecting device 100 projects the blasting medium 400 again. Then, the projecting device 100 adds, to the distributor 110 at a predetermined timing, an unused blasting medium 400 in an amount equivalent to a decrease due to exclusion of the blasting medium 400. However, even the blasting medium 400 that is suitable to be reused has a particle size which is gradually reduced by wear. Furthermore, addition of the unused blasting medium 400 abruptly changes an average particle size of the blasting medium 400 that passes through the gate 111. This makes it necessary to adjust the degree of opening of the gate 111 in order to stabilize a flow rate of the blasting medium 400 that is supplied to the impeller 120.
In a case where the gate 111 is rotary, the degree of opening of the gate 111 is expressed by an angle. In Embodiment 1, for example, a change in degree of opening of the gate 111 by 1° corresponds to a change in position of the cylinder 112 by 1 mm. The servo motor 113 finely adjusts the degree of opening of the gate 111 by changing the position of the cylinder 112. The servo motor 113 has a range of motion of, for example, 50 mm, and can change the position of the cylinder 112 in 0.01 mm unit to 1 mm unit.
The impeller 120 projects the blasting medium 400 to the projection target object 500 by a motor 121. The motor 121 has a load current value that has a positive correlation with an amount of the blasting medium 400 which is supplied to the impeller 120. That is, in a case where the blasting medium 400 is supplied in a small amount, a low load is applied to the impeller 120, so that the motor 121 has a small load current value. In a case where the blasting medium 400 is supplied in a large amount, a high load is applied to the impeller 120, so that the motor 121 has a large load current value. Thus, the blasting medium 400 can be supplied in an appropriate amount by controlling the degree of opening of the gate 111 in accordance with the load current value of the motor 121.
By thus causing the servo motor 113 to precisely carry out position control with respect to the cylinder 112, the degree of opening of the gate 111 can be changed with high accuracy, and a lower limit of a shot amount can be adjusted with high accuracy. This makes it possible to properly maintain a projection quality and reduce a probability with which the projection target object 500 will be a defective product. It is assumed in
The current transformer 122 measures the load current value of the motor 121 and transmits the load current value to the PLC 200 via a communication interface (I/F) 211.
The PLC 200 controls the projecting device 100. The PLC 200 is connected to sections of the projecting device 100 and controls the projecting device 100. The PLC 200 includes the communication I/F 211, a storage section 212, a processor 213, and an output-input I/F 214. The communication I/F 211, the storage section 212, the processor 213, and the output-input I/F 214 are connected to each other via a bus.
Various information devices such as a meter (not illustrated) are connected to the communication I/F 211 via a communication network. In Embodiment 1, the communication network is an analog circuit such as a wired LAN. Alternatively, the communication network may be, for example, Ethernet (registered trademark), Wi-Fi (registered trademark), or CC-Link (registered trademark), or may be implemented in a cloud.
The storage section 212 stores, for example, the following information:
Examples of a device that can be used as the storage section 212 include a flash memory.
The processor 213 receives current value data from the current transformer 122, reads the above various pieces of information from the storage section 212, and determines an appropriate control position of the servo motor 113. In a case where the load current value of the motor 121 reaches a correction current lower limit CC1, the processor 213 drives the servo motor 113 in accordance with the control position so as to adjust the position of the cylinder 112 and consequently to adjust the degree of opening of the gate 111.
To the output-input I/F 214, an input device and/or an output device is/are connected. Examples of the output device that is connected to the output-input I/F 214 include a display and a printer. Examples of the input device that is connected to the output-input I/F 214 include a mouse and a keyboard. The output-input I/F 214 may be, for example, an HDMI (registered trademark) or a USB (registered trademark). In Embodiment 1, the output-input device 300 serving as the output device is connected to the output-input I/F 214.
The output-input device 300 displays various pieces of information transmitted from the PLC 200, and receives various input operations performed by a user. The output-input device 300 may be, for example, a device with respect to which output and input can be carried out, such as a touch panel, or a combination of an output device such as a display and an input device such as a button. Furthermore, the output-input device 300 may include a warning device (not illustrated).
The following description will discuss, with reference to
The current lower limit CLI is a current value that enables the projecting device 100 to surface-treat the projection target object 500 while maintaining a quality that exceeds a minimum quality. An amount of the blasting medium 400 to be projected per unit surface area of the projection target object 500 is referred to as a projection density. The projection density affects a projection quality, and a projection density that is not less than the current lower limit CL1 is necessary to maintain a predetermined projection quality. When the projection density is a minimum projection density that maintains the predetermined projection quality, the load current value of the motor 121 is measured as a value of the current lower limit CL1.
The current upper limit CL2 is a current value upper limit for preventing an excessive load from being applied to components of the projecting device 100, in particular, the motor 121 of the impeller 120. Note, however, that the current upper limit CL2 need not be set. The correction current lower limit CC1 is a current value for the projecting device 100 to surface-treat the projection target object 500 while maintaining a good quality. Note, however, that the correction current lower limit CC1 need not be set. The correction current upper limit CC2 is a current value upper limit for preventing the projecting device 100 from using excessive electric power during projection. Note, however, that the correction current upper limit CC2 need not be set. The current lower limit CL1, the current upper limit CL2, the correction current lower limit CC1, and the correction current upper limit CC2 each may be obtained by adding or subtracting a predetermined value to/from the target current value CT, or may be obtained by multiplying the target current value CT by a predetermined ratio. The predetermined ratio may be, for example, a predetermined ratio with respect to a maximum current value of the motor 121 at shipment from a factory. The target current value CT and the other four values, i.e., the current lower limit CL1, the current upper limit CL2, the correction current lower limit CC1, and the correction current upper limit CC2 may be determined by, for example, receiving, whenever necessary, operations performed by the user. Furthermore, the current value may be determined to be “not less than” or “not more than” the upper limit or the lower limit, or may be determined to be “more than” or “less than” the upper limit or the lower limit.
Upon starting of the motor 121 of the projecting device 100, the load current value of the motor 121 increases to a starting current value in a very short period of time and then decreases toward a non-load current value. At a time point to, where the current value of the motor 121 is stabilized, the processor 213 starts projection. The load current value of the motor 121 is unstable for a certain period of time after the processor 213 starts projection. After that, however, the load current value of the motor 121 is stabilized and fluctuates at approximately the target current value CT. However, the load current value of the motor 121 increases or decreases due to various causes such as wear and/or addition of the blasting medium 400. A decrease in load current value of the motor 121 causes the load current value of the motor 121 to be less than the correction current lower limit CC1 at a time point t′1. Thereafter, the load current value of the motor 121 increases. At a time point t′2, the load current value of the motor 121 is more than the correction current upper limit CC2. Thereafter, the load current value of the motor 121 decreases. Upon completion of projection by the projecting device 100, the load current value of the motor 121 decreases to the non-load current value. Thus, in a case where the processor 213 does not carry out control, a change in state of the blasting medium 400 may cause the load current value of the motor 121 to be less than the correction current lower limit CC1, so that the projection target object 500 may be prevented from having a good quality.
In a step S101, the processor 213 reads, from the storage section 212, an initial value of the degree of opening of the gate 111. Note that the processor 213 may read, instead of the degree of opening of the gate 111, the position of the cylinder 112, the position having been adjusted by the servo motor 113. Regarding the degree of opening of the gate 111, same applies to the following description.
In a step S102, the processor 213 places the cylinder 112 in the state of opening the gate 111.
In a step S103, the processor 213 drives the servo motor 113 to adjust the position of the cylinder 112 so that the degree of opening of the gate 111 reaches the initial value.
In a step S104, the processor 213 starts projection by the projecting device 100. The load current value of the motor 121 is temporarily unstable at the commencement of projection. Thus, in order to prevent such an unstable load current value from being determined, the processor 213 may wait for a certain period of time before carrying out a step S110.
The processor 213 repeatedly carries out the step S110 to a step S145 for each predetermined sampling cycle. In the motor 121, a chattering phenomenon may occur in which the current value repeatedly violently fluctuates in a short period of time. In order to efficiently carry out the control process without reference to such a violently fluctuating current value, the sampling cycle is desirably an interval that is so short as not to be affected by chattering, e.g., several seconds to several minutes. For example, in a case where a continuous process is carried out or in a case where the blasting medium 400 has a high flow rate and a change in particle size caused by, for example, wear less occurs, according to the shot-blasting device 1, the load current value of the motor 121 is gradually displaced. Thus, it is recommended that the sampling cycle in which a change is detected be gradually changed in minutes. For example, a case where surface texture of the projection target object 500 is drastically changed or a case where the blasting medium 400 has a low flow rate results in a great change in the load current value of the motor 121. Thus, in some cases, the sampling cycle in which a change is detected is desirably every several seconds to several tens of seconds. A proper sampling cycle varies depending on a mechanism for collecting the blasting medium 400, a frequency at which the blasting medium 400 is added, a configuration of the shot-blasting device 1, and/or a type of the projection target object 500. The processor 213 may use, for example, PID control as another method that is not affected by chattering. Note, however, that the another method is not limited to the PID control.
In the step S110, the processor 213 determines whether the projection has been completed in the projecting device 100. In a case where projection has been completed (YES in the step S110), the processor 213 ends the control process. In a case where the projection has not been completed (NO in the step S110), the processor 213 carries out the step S120.
In the step S120, the processor 213 determines whether the load current value of the motor 121 of the impeller 120 is not more than the correction current lower limit CC1 or not less than the correction current upper limit CC2. In a case where the load current value of the motor 121 is not more than the correction current lower limit CC1, the processor 213 carries out the step S130. In a case where the load current value of the motor 121 is not less than the correction current upper limit CC2, the processor 213 carries out the step S140. In a case where the load current value of the motor 121 is more than the correction current lower limit CC1 and less than the correction current upper limit CC2 (“MORE THAN CORRECTION CURRENT LOWER LIMIT AND LESS THAN CORRECTION CURRENT UPPER LIMIT” in the step S120), the processor 213 continues to wait until the next sampling cycle.
In the step S130, the processor 213 determines whether the load current value of the motor 121 is not more than the current lower limit CL1. In a case where the load current value of the motor 121 is not more than the current lower limit CL1, the processor 213 carries out the step S131. In a case where the load current value of the motor 121 is more than the current lower limit CL1, the processor 213 carries out the step S135.
In the step S131, the processor 213 issues a warning via a warning device 310. A case where the load current value of the motor 121 is not more than the current lower limit CL1 indicates that the projection density falls below a projection density for maintaining the minimum quality of the projection target object 500. A case where the current value of the motor of the impeller 120 is less than the current lower limit CL1 occurs because the projection target object 500 is highly likely to be a defective product due to the insufficient projection density. Thus, the processor 213 may end projection by the projecting device 100.
In the step S135, the processor 213 determines the control position of the servo motor 113 so that the load current value of the motor 121 is greater than the correction current lower limit CC1.
In accordance with a period of time until the blasting medium 400 reaches the impeller 120 from the gate 111, it takes time until adjustment of the degree of opening of the gate 111 is reflected in the load current value of the motor 121. Thus, in accordance with the period of time until the blasting medium 400 reaches the impeller 120 from the gate 111, the processor 213 sets the amount of change per unit time in the servo motor 113 in advance, for example, during installation of the distributor 110. The processor 213 may drive the servo motor 113 by the amount of change per unit time until, for example, a position of the servo motor 113 reaches a control target value, the control target value being stored in the storage section 212 in advance as the degree of opening of the gate 111, the degree being necessary to change the load current value of the motor 121 to the target current value CT. Alternatively, the processor 213 may determine a control target value of the servo motor 113 from a difference between the load current value of the motor 121 and the correction current lower limit CC1 or a difference between the load current value of the motor 121 and the target current value CT. Note that the processor 213 may drive the servo motor 113 by the amount of change per unit time until the load current value of the motor 121 reaches the target current value CT.
In the step S136, the processor 213 drives the servo motor 113 to the determined control position so that the degree of opening of the gate 111 is adjusted. That is, the servo motor 113 that has received a command of the processor 213 gradually moves the cylinder 112, in accordance with the amount of change per unit time, in a direction in which the degree of opening of the gate 111 is increased.
In the step S140, the processor 213 determines whether the current value of the motor of the impeller is not less than the current upper limit CL2. In a case where the load current value of the motor 121 is not less than the current upper limit CL2, the processor 213 carries out the step S141. In a case where the load current value of the motor 121 is less than the current upper limit CL2, the processor 213 carries out the step S145.
In the step S141, the processor 213 issues a warning via the warning device 310. This is because in a case where the load current value of the motor 121 is not less than the current upper limit CL2, an excessive load is highly likely to be applied to the projecting device 100.
In the step S145, the processor 213 determines the control position of the servo motor 113 so that the load current value of the motor 121 is smaller than the correction current upper limit CC2. The control position of the servo motor 113 is determined as in the case of the step S135. The processor 213 may determine the control target value of the servo motor 113 from a difference between the load current value of the motor 121 and the correction current upper limit CC2 or a difference between the load current value of the motor 121 and the target current value CT.
In a step S146, the processor 213 drives the servo motor 113 in accordance with the calculated amount of change per unit time so that the degree of opening of the gate 111 is adjusted. That is, the servo motor 113 that has received a command of the processor 213 gradually moves the cylinder 112, in accordance with the amount of change per unit time, in a direction in which the degree of opening of the gate 111 is reduced.
Furthermore, the above configuration makes it possible to reduce an amount of emission of carbon dioxide generated in a manufacturing process. Such an effect also contributes to achievement of, for example, Goal 13 “Take urgent action to combat climate and its impacts” of Sustainable Development Goals (SDGs) proposed by the United Nations.
The following description will discuss another embodiment of the present invention. Note that for convenience, members having functions identical to those of the respective members described in Embodiment 1 are given respective identical reference numerals, and a description of those members is omitted.
The processor 213 can store, in the storage section 212, any or a combination of the current lower limit CL1 or the current upper limit CL2, the correction current lower limit CC1, and the correction current upper limit CC2 as a plurality of patterns. Such storage may be carried out before operation of the projecting device 100 commences. Alternatively, while the projecting device 100 is in operation, the processor 213 may carry out the storage automatically or upon receiving an operation performed by the user. Before operation of the projecting device 100 commences or while the projecting device 100 is in operation, the processor 213 may read, from the plurality of patterns stored in the storage section 212, the current lower limit CL1, the current upper limit CL2, the correction current lower limit CC1, and the correction current upper limit CC2, which are used to carry out determination in the step S120, the step S130, and the step S140 in
This enables a single projecting device 100 to carry out proper projection with respect to a plurality of types of the projection target object 500, so that a projection process can be carried out more efficiently. For example, a case where the projection target object 500 is a casting and a case where the projection target object 500 is a steel wire differ in required projection quality, and thus differ in the current lower limit CL1. However, the above configuration enables a single shot-blasting device 1 to carry out projection, while maintaining a proper quality, in both the case where the projection target object 500 is a casting and the case where the projection target object 500 is a steel wire.
The following description will discuss a further embodiment of the present invention. Note that for convenience, members having functions identical to those of the respective members described in Embodiments 1 and 2 are given respective identical reference numerals, and a description of those members is omitted.
The processor 213 may store, in the storage section 212, the degree of opening of the gate 111 as time series data. The time series data is compared with time series data, separately stored by the storage section 212, on the load current value of the motor 121 so as to serve as recorded data on control carried out by the processor 213.
This configuration enables records of quality control of the projection target object 500 through control of the load current value of the motor 121 by a change in degree of opening of the gate 111 to be left and traceable. Furthermore, by collecting and analyzing these records as, for example, big data, it is possible to set projection more efficiently.
Functions of the shot-blasting device 1 (hereinafter referred to as a “device”) can be realized by a program for causing a computer to function as the device, the program causing the computer to function as control blocks (in particular, sections of a processor) of the device.
In this case, the device includes, as hardware for executing the program, a computer including at least one control device (e.g., a processor) and at least one storage device (e.g., a memory). The functions described in the above embodiments are realized by the program being executed by the at least one control device and the at least one storage device.
The program may be recorded in one or more non-transitory computer-readable recording media. The recording media may be included in the device or need not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.
Furthermore, some or all of functions of the control blocks can also be realized by a logic circuit. For example, the scope of the present invention also encompasses an integrated circuit in which a logic circuit that functions as the control blocks is provided. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.
The processes described in the above embodiments may be carried out by artificial intelligence (AI). In this case, AI may be operated in the control device, or may be operated in another device (e.g., an edge computer or a cloud server).
The present invention is not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims. The present invention also encompasses, in its technical scope, any embodiment derived by combining technical means disclosed in differing embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-212829 | Dec 2022 | JP | national |
